feat: Add optional web interface authentication with session management

Authentication Features:
  - Optional HTTP Basic Auth with session cookies for web interface protection
  - Configurable username/password with session timeout (default: 1 hour)
  - Selective route protection (web interface protected, webhooks/APIs remain public)
  - Authentication status display with logout functionality in web UI
  - Session cleanup and graceful logout with browser re-authentication prompt

  Configuration:
  - WEB_AUTH_ENABLED in .env (default: false - no breaking changes)
  - WEB_AUTH_USERNAME/WEB_AUTH_PASSWORD in .env.secrets
  - WEB_AUTH_SESSION_TIMEOUT configurable (5min-24h range)

  Development Tools:
  - Added debug_tv.py for TV series/episode debugging (series, season, episode levels)
  - Comprehensive episode data inspection with validation and sources breakdown
  - Complements existing debug_movie.py for complete media debugging coverage

  Technical Implementation:
  - SimpleAuthMiddleware with FastAPI integration
  - Session management with automatic cleanup
  - Authentication status API endpoints
  - Responsive CSS styling for auth UI elements
  - JavaScript functions for auth checking and logout

api/routes.py

@@ -7,7 +7,7 @@ import requests
 import asyncio
 from pathlib import Path
 from datetime import datetime, timezone
-from fastapi import HTTPException, BackgroundTasks, Request
+from fastapi import HTTPException, BackgroundTasks, Request, Response
 from typing import Optional
 
 # Import models
@@ -1396,6 +1396,38 @@ def register_routes(app, dependencies: dict):
         """Update episode dateadded"""
         return await update_episode_date(dependencies, imdb_id, season, episode, request.dateadded, request.source)
     
+    @app.post("/api/auth/logout")
+    async def _logout(request: Request, response: Response):
+        """Logout endpoint - clears session"""
+        session_manager = dependencies.get("session_manager")
+        if session_manager:
+            session_token = request.cookies.get("nfoguard_session")
+            if session_token:
+                session_manager.delete_session(session_token)
+        
+        response.delete_cookie("nfoguard_session")
+        return {"status": "logged_out", "message": "Session cleared"}
+    
+    @app.get("/api/auth/status")
+    async def _auth_status(request: Request):
+        """Check authentication status"""
+        auth_enabled = dependencies.get("auth_enabled", False)
+        
+        if not auth_enabled:
+            return {"authenticated": True, "auth_enabled": False, "message": "Authentication disabled"}
+        
+        session_manager = dependencies.get("session_manager")
+        if not session_manager:
+            return {"authenticated": False, "auth_enabled": True, "message": "Session manager not available"}
+        
+        session_token = request.cookies.get("nfoguard_session")
+        if session_token:
+            username = session_manager.get_session_user(session_token)
+            if username:
+                return {"authenticated": True, "auth_enabled": True, "username": username}
+        
+        return {"authenticated": False, "auth_enabled": True, "message": "Not authenticated"}
+
     @app.post("/api/bulk/update-source")
     async def _bulk_update_source(request: BulkUpdateRequest):
         """Bulk update source for movies or episodes"""